1. Field of the Invention
The present invention is related to an improved structure of filtering bag combination, and especially to an improved structure of filtering bag combination having a good filtering effect, an increased area of filtering and a longer life of use, it suits filtering equipments for various industrial dust collecting systems.
2. Description of the Prior Art
Air pollution can have the polluting materials divided into granular and gas type materials, while the methods for controlling air-polluting materials can also be divided into three kinds of modes. The first mode is the conventional mode; it increases the height of a chimney or renders a factory to move away from an area where population of people is large. Such mode can only solve the problem of air pollution of the area near the factory; this is because that the gross amount of the polluting materials discharged to the atmosphere is unchanged. Particularly the gas SO2, it always is delivered to areas thousand kilometers away and then generates the problem of precipitation of sour rains. The second mode is to add a control equipment before gas is discharged from a pollution source to remove a part of polluted materials before discharging the gas. The concentration of the discharged polluted materials shall meet the statutory standard of discharging in order not to influence the standard of quality of the air in the atmosphere; the removed polluted materials can be recycled for using sometimes. The third mode is the most effective way, this is to change the method and the process of production to inhibit generation of air polluting materials or to lower the concentration of the air polluting materials to a degree to render them unnecessary to be processed before discharging; however, this mode shall consider the problem of the cost of production.
Generally, by the fact that the cost of production and the efficiency of removing the polluting materials shall be both in consideration, people in the art are more often to adopt the second mode; while control equipments can be divided into treatment equipments for granular and gas type materials. Equipments for removing granular materials take advantages of one or some of the following actions: gravity, inertia, centrifugal force, diffusion, filtering, acoustic wave or stationery electric force; they separate and collect particles in the gas, and then discard or reuse them. Taking a usual bag type dust collector as an example, it mainly renders the particles such as of dust etc. to be isolated outside the filtering member after the polluted gas passing the filtering member provided on the dust collector, and cleaner air can be obtained. Usual dust collecting filtering bags can be divided into elongate and cylindrical shape in pursuance of the types of the dust collectors.
By virtue that filtering members are very important in processes of filtering, conventional dust collecting filtering bags can be divided into two kinds, namely a fixed type and a soft type. A bag of the fixed type is made of ventilating molded foam, the structure of the bag is stiff and abrasion durable and can be spray washed, thereby it has a long life of use, a good filtering effect, but it is very expensive; while a filtering bag of the soft type is cheaper, the filtering member it uses is just paper or ventilating cloth; in designing filtering bags, paper or non-woven fabric is used to make an elongate cylinder or a normal cylinder which is slipped over a support; and in practicing, dirt air will pass the cylinder to screen off the particles and dust. However, such filtering mode has a fixed area of filtering, its filtering effect and life of use are extremely limited; therefore, conventional techniques all make the filtering members folded to surround and envelop a support in order to increase the surface area of the filtering members.
However, the conventional filtering bags still have the following flaws:    1. Conventional filtering members can increase the surface area of filtering by folding, however relatively, the papers are thinner and are not so durable for abrasion; and in practicing, they are connected with air exhausting and absorption devices with strong powers, the filtering members are subject to abrasion and damage during exhausting and absorption to thereby shorten the lives of use of them.    2. The filtering members all have folded angles after folding, the folded areas form serrated crests and hollows, they are unable to be unfolded and thereby become dead corners of filtering, dust and particles will be attached to these folded areas and are hard to be removed by tapping; the filtering members are subject to being blocked in use and thereby have their lives of use affected, further by nonstop abrasion of the dust and particles against the dead corners during air exhausting and absorption, this can speedy damage and further shorten the lives of use of the filtering members.    3. Generally, durability against abrasion of non-woven fabric is better than that of paper, but non-woven fabric is softer and thicker, it can not have a fixed shape after folding and even after folding, it is still loose; hence conventional filtering bags made of non-woven fabric can only be made into cylindrical shape rather than being pleated into multiple folds, their filtering areas are too small, they need to be changed often, otherwise, a dust collector shall be enlarged to meet the required filtering area of the filtering bag when in manufacturing the dust collector.